Method of detecting valve timing

ABSTRACT

A method and apparatus for detecting a valve position includes the step of providing a non-actuating alternating current signal ( 24 ) to a drive coil signal ( 22 ). As a valve plunger ( 14 ) moves within the coil, the non-actuating signal changes. By monitoring ( 26,29 ) the non-actuating signal a control can predict when the plunger reaches a particular position. This invention thus provides a simplified way of detecting an end of travel position (FIG.  1 ).

[0001] This application claims priority to Provisional PatentApplication Ser. No. 60/223,946 filed Aug. 9, 2000.

BACKGROUND OF THE INVENTION

[0002] This application relates to a method for detecting valve positionin a valve driven by at least one electromagnetic coil, wherein changesin a signal applied to the coil are sensed.

[0003] For purposes of this application, the term “coil” will refer toany type of device such as a solenoid, etc., which receives an electricsignal to in turn move a plunger. The plunger may be a permanent magnet,or simply a material such as iron which is subject to magneticattraction.

[0004] Valves are typically utilized in vehicle engines to control thesupply of fuel and air to the engine cylinders. One type of valve isdriven by a pair of coils, and is utilized as part of a fuel injector.In such a valve the two coils are selectively and alternatively poweredto drive the plunger between two positions and control the supply offuel. With such systems, it is very difficult to accurately track thetiming of the valve, and to determine its position as it moves.

[0005] Other types of valves are driven by a single coil in onedirection, and moved in the other direction by a spring force. The sameconcerns with regard to tracking the movement of the plunger exists inthese systems.

[0006] Another application for vehicle control is the air supply andexhaust valves on an engine. Historically these valves have beencontrolled to open in sequence by a cam shaft and rocker arms. Morerecently camless control systems have been utilized. However, thesecamless systems have the same problem as mentioned above with regard todetection of the actual position of the valve plunger.

[0007] The present invention provides a simple method for detectingplunger position.

SUMMARY OF THE INVENTION

[0008] In a disclosed method and apparatus of this invention, twosignals are supplied to a coil for driving a valve plunger. A firstactuating signal powers the coil to drive the plunger. A secondnon-actuating signal is applied to at least one coil associated with theplunger. As the plunger moves, it will produce changes in thisnon-actuating signal. These changes are identified by a control suchthat by monitoring the changes the system will be able to predict atleast when the plunger has approached an end of travel position. Mostpreferably, the change is compared to a reference signal.

[0009] In one embodiment there is only one coil for powering theplunger. In a second embodiment there are a pair of spaced coils. Inthis embodiment the non-actuating signal could be applied to theactivated coil, or the deactivated coil.

[0010] In the embodiment having two drive coils, it could be thenon-actuated coil which is utilized to provide the reference. Inparticular, a valve plunger other than the one that is being driven mayalso have a non-actuating signal applied to one of its coils. Thechanges in that signal are compared to the changes in the signal fromthe moving plunger coil. In this way, the system is better able toaccurately track when changes in the non-actuating signal are in factindicative of an end of travel position.

[0011] These and other features of the present invention can be bestunderstood from the following specification and drawings, and thefollowing which is a brief description.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012]FIG. 1 shows a first embodiment of the invention.

[0013]FIG. 2 shows another embodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0014] As shown in FIG. 1, valve 10 including a plunger 14 which isspring biased by a spring 16 to a position where it blocks flow througha fluid path 18. A coil 15 is selectively actuated to pull the plungerin an opposed direction. As illustrated, a DC actuating circuit 22 andan AC supply circuit, such as an oscillator, 24, apply both an actuating(DC) and a non-actuating (AC) signal to the coil 15. A phase shiftdetector 26 detects any change in the phase supplied by the AC source24, which may be modified by the movement of the plunger 14. A secondsignal is taken from a second reference source 27, which could be aplunger which is non-actuated. As an example, these systems aretypically employed in internal combustion engines having a number ofcylinders, and there are typically several of the plungers which wouldbe non-actuated. Reference signal source 27 may be taken from one ofthose non-actuated plungers. The signals from both a non-actuated systemphase shift detector 28 and phase shift detector 26 associated with theactivated system are both supplied to a control 29. In the disclosedembodiment, the control 29 has differentiating applier 31, adifferentiator 30 and in turn to a microprocessor control 32. Thecontrol is shown as partially hardware, but of course all of these stepscan also be taken in software within the scope of this invention.Essentially, the system compares the change in phase shift between thetwo phase shift detectors, and if a significant difference exists, thena determination can be made that the plunger is at a particularposition.

[0015] Applicant has learned that when movement of the plunger begins orwhen it approaches an end of travel position, there are distinct changesin the super imposed AC signal that the detectors from the two coilswill be able to detect. As the plunger moves, the phase will change, andthe phase shift detector will detect those changes. Alternatively, theamplitude or frequency could also be monitored for change. By monitoringthese changes as the plunger is moved, the inventor of this system haslearned it can identify particular points during the movement path ofthe plunger.

[0016] By utilizing the reference plunger 27 which is non-actuated, thesystem is able to eliminate “noise” or other false indications of aparticular point in travel, that could have been erroneously based upona change in the signal for some reason other than plunger position. Asan example, vibration, or other variables that will be experienced bythe vehicle could also result in a phase shift. By looking at thenon-actuated plunger, the system is able to filter out any such falsereadings. That is, if the non-actuated plunger is undergoing a similarphase shift to the one in the plunger being monitored, then the controlwill be able to identify that it is not an end of travel position butinstead some other variable which has caused the phase shift.

[0017] As shown in FIG. 2, another common type plunger has two drivecoils rather than a spring. The drive coils 40 and 42 are selectivelyactuated to move the plunger 44 between two positions. Each of the twocoils is provided with its own drive circuit 50, and those two circuitssend signals from phase shift detectors to a control 52. The circuit 50and control 52 may be generally as shown in FIG. 1. This two-coil systemcould also be monitored by taking a reference from another non-actuatedplunger.

[0018] Moreover, it may be that a certain expected phase shift for aparticular point in the plunger movement could be stored in a control,rather than requiring comparison with a reference. However, it ispreferred that the reference signal be utilized. Finally, while thenon-actuated signal is preferably applied to the coil which is actuated,it may also be applied to the non-actuated coil, and it would beexpected that some change would occur even in the non-actuated coil asthe plunger moves.

[0019] The aforementioned description is exemplary rather then limiting.Many modifications and variations of the present invention are possiblein light of the above teachings. The preferred embodiments of thisinvention have been disclosed. However, one of ordinary skill in the artwould recognize that certain modifications would come within the scopeof this invention. Hence, within the scope of the appended claims, theinvention may be practiced otherwise than as specifically described. Forthis reason the following claims should be studied to determine the truescope and content of this invention.

What is claimed is:
 1. A method of detecting valve movement comprisingthe steps of: a) actuating a coil through an actuating signal to drive aplunger to move a valve; b) imposing a nonactuating signal; c) detectinga change in the nonactuating signal as the plunger moves; and d)determining a plunger position based upon the detected change.
 2. Themethod of claim 1 wherein the nonactuating signal comprises analternating current.
 3. The method of claim 1 wherein the change iscompared to a reference signal.
 4. The method of claim 1 wherein asingle coil drives said plunger, and both the actuating andnon-actuating signals are sent to said single coil.
 5. The method ofclaim 1 wherein a pair of coils drives said plunger, with one of saidcoils being powered by an actuating signal to drive said plunger in eachof two opposed directions and the other being deactivated.
 6. The methodof claim 5 wherein said non-actuating signal is applied to the coilwhich is being supplied with said actuating signal.
 7. The method ofclaim 5 wherein said coil which receives said actuating signal does notreceive said non-actuating signal, and said non-actuating signal beingsent to said deactivated coil.
 8. The method of claim 1 including thestep of comparing the change in nonactuating signal to a referencesignal.
 9. The method of claim 8 wherein the reference signal isobtained from a reference plunger.
 10. A method of controlling a valveincluding the steps of: a) providing a first coil for driving a plungerin a first direction; b) providing a second coil for driving saidplunger in a second direction; c) providing a control for alternativelysupplying an actuating signal to each of said first and second coils todrive said plunger in opposed directions; d) imposing an alternatingcurrent non-actuating signal on one of said two coils and imposing anactuating signal on one of said coils; and e) detecting a change in saidnon-actuating alternating current as said electromagnetic plunger moves,and identifying a particular position based upon said change in saidnon-actuating signal.
 11. The method of claim 10 wherein saidnon-actuating signal is applied to said coil which also receives saidactuating signal.
 12. The method of claim 10 wherein said non-actuatingsignal is supplied to a coil which does not receive said actuatingsignal.
 13. The method of claim 10 including the step of comparing thechange in impedance to a reference impedance.
 14. The method of claim 13wherein the reference impedance is obtained from a referenceelectromagnetic plunger.
 15. A drive system for a valve comprising: aplunger connected to move with a valve; at least one coil for drivingsaid plunger in a first direction, and a drive circuit for supplying anactuating signal to said coil; a source to supply an alternatingnon-actuating signal; and a sensor for sensing changes in saidnon-actuating signal as said plunger moves.
 16. A valve system asrecited in claim 15 wherein said non-actuating signal is supplied tosaid one coil while it is receiving said actuating signal.
 17. A valvesystem of claim 15 wherein there is a pair of coils which drive saidplunger in opposed directions.
 18. The valve system of claim 17 whereinsaid coil which receives said actuating signal also receives saidnon-actuating signal.
 19. The valve system of claim 17 wherein said coilwhich is not receiving said actuating signal receives said non-actuatingsignal.
 20. A valve system as recited in claim 15 wherein said sensorcompared said change in said non-actuating signal to a reference signalfrom another valve system.